dreamchain

rApache on Debian 6.0 squeeze or Ubuntu 10.04 Lucid Lynx

Simon — Wed, 07 Mar 2012 13:38:33 +0000

This is how I installed and configured rApache on Debian 6.0 (squeeze). It should work on Ubuntu 10.04 Lucid Lynx also.

Install R and Apache MPM prefork (I assume that Apache 2 is installed already):


> sudo aptitude install r-base r-base-dev apache2-mpm-prefork apache2-prefork-dev

Download and build rApache from source:


> cd /usr/local/src
> sudo wget http://biostat.mc.vanderbilt.edu/rapache/rapache-1.1.17.tar.gz
> sudo tar xzf rapache-1.1.17.tar.gz
> cd rapache-1.1.17
> sudo ./configure
> sudo make
> sudo make install

Create file /etc/apache2/mods-available/R.load with content:


LoadModule R_module /usr/lib/apache2/modules/mod_R.so

Enable mod_R:


> sudo a2enmod R

Create folder /var/www/r-scripts .

Add the following to /etc/apache2/sites-available/default inside :



	...
	
		SetHandler r-script
		RHandler sys.source
	
	...

Created file /var/www/r-scripts/hello.R with the following content:


setContentType(type='text/plain')
cat('Hello')
DONE

Restart Apache:


sudo /etc/init.d/apache2 restart

Verify that it works:


wget -qO- http://localhost/r-scripts/hello.R
Hello

Done.

References:

http://rapache.net/manual.html

Apache Server, Tomcat and mod_jk on Debian 6.0 squeeze

Simon — Wed, 07 Mar 2012 08:14:17 +0000

This is how I integrated Tomcat 6 with Apache 2 on Debian 6.0 (squeeze) using mod_jk. It should also work on Ubuntu 10.04 Lucid Lynx.

Install Apache Web Server:


> aptitude install apache2

Verify that the server is running:


> wget -qO- http://localhost | head -1
It works!

Install Tomcat (you don’t need to install tomcat6-examples, I did it only for the purpose of this How To):


> aptitude install tomcat6 tomcat6-examples

Verify that Tomcat server is running:


> wget -qO- http://localhost:8080 | head -11 | tail -1
It works !

Install mod_jk:


> aptitude install libapache2-mod-jk

Create file /etc/apache2/workers.properties with the following content:


worker.list=worker1
worker.worker1.type=ajp13
worker.worker1.host=localhost
worker.worker1.port=8009

Create file /etc/apache2/mods-available/jk.conf with the following content:


JkWorkersFile	/etc/apache2/workers.properties
JkShmFile	/var/log/apache2/mod_jk.shm
JkLogFile	/var/log/apache2/mod_jk.log
JkLogLevel	info

Enable jk conf:


> a2enmod jk

Add mount point to /etc/apache2/sites-available/default:



	...
	JkMount		/examples/* worker1
	...

Uncomment the following line in /etc/tomcat6/server.xml:

Restart Tomcat:


> /etc/init.d/tomcat6 restart

Restart Apache web server:


> /etc/init.d/apache2 restart

Now verify that everything works:


> wget -qO- http://localhost/examples/ | tail -7 | head -1
Apache Tomcat Examples

Done.

Here is a complete script for setting up Apache 2, Tomcat 6 and mod_jk on Ubuntu 10.04.

References:

http://tomcat.apache.org/connectors-doc/generic_howto/quick.html

MacPorts, Clojure and ClassNotFoundException

Simon — Wed, 11 Jan 2012 11:15:14 +0000

After installing Clojure with MacPorts I got the following exception when running a basic Clojure script:


Exception in thread "main" java.lang.NoClassDefFoundError: Pad:/opt/local/share/java/clojure/bin////lib/clojure/jar
Caused by: java.lang.ClassNotFoundException: Pad:.opt.local.share.java.clojure.bin....lib.clojure.jar
	at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

As it turned out, I had run the script from a folder with a space in it’s name, “Scratch Pad”. After moving the script to an other folder, the script ran just fine.

Grails, CoffeeScript and Eclipse

Simon — Sun, 30 Oct 2011 00:49:29 +0000

I’m using the Grails CoffeeScript plugin, but when running my Grails application from Eclipse, with run-app, I got the following error:


Compiling CoffeeScript Files ...ERROR Launching CoffeeScript compiler: Cannot run program "coffee": error=2, No such file or directory

Now, in order to fix this you need to tell the CoffeeScript Grails plugin where to find the coffee command. You can do this in BuildConfig.groovy by adding this line:


grails.coffeescript.compiler.location="/opt/local/bin/coffee"

But, this is not enough, because now I get the following error:


Compiling CoffeeScript Files ...env: node: No such file or directory

The solution I found to this problem was editing /opt/local/bin/coffee, changing


#!/usr/bin/env node


#!/opt/local/bin/node

Now I’m able to do run-app from within Eclipse.

Keep in mind that I’m on a Mac having installed CoffeeScript with npm, and node and npm with MacPorts. You might have your CoffeeScript installation in a different location.

Port forwarding from port 80 to port 8080 with iptables

Simon — Mon, 24 Oct 2011 16:01:44 +0000

If you need to do port forwarding from port 80 to port 8080 (maybe you are running tomcat on port 8080) you can do it with iptables like this:


sudo iptables -A PREROUTING -d $HOSTNAME -p tcp --dport 80 -j REDIRECT --to-ports 8080 -t nat

If you want to revert the change to iptables do this:


sudo iptables -F -t nat

max-width and height: auto for images in IE8

Simon — Fri, 21 Oct 2011 21:49:22 +0000

In IE8, if you have an image with the following markup and css:

img {
	width: 100%;
	max-width: 400px;
	height: auto;
}

the image height is going to grow past 300px in non-compatibility view!

In order to fix this issue add max-height: 300px; to the css.

How to sync MacPorts without rsync

Simon — Fri, 21 Oct 2011 21:31:32 +0000

If port 873 is blocked on your network and you need to sync MacPorts do this:

In /opt/local/etc/macports/sources.conf replace


rsync://rsync.macports.org/release/ports/ [default]

with


http://www.macports.org/files/ports.tar.gz [default]

and run


sudo port sync

instead of


sudo port selfupdate

MacPorts is now synching using http over port 80 instead of rsync over port 873.

Tuckey rewrite rule has new default value

Simon — Thu, 30 Jun 2011 16:11:36 +0000

After upgrading from Tuckey UrlRewrite 3.0 to 3.1 I noticed that the default value for the last attribute has changed from true to false, so I had to do some small changes to the xml configuration.

Old rules:



	
		/images/**
		/images/$1
	
	
		/scripts/**
		/scripts/$1
	
	
		/styles/**
		/styles/$1
	
 	
		/**
		/app/$1
	
	
		/app/**
		/$1

New rules:



	
		/images/**
		/images/$1
	
	
		/scripts/**
		/scripts/$1
	
	
		/styles/**
		/styles/$1
	
 	
		/**
		/app/$1
	
	
		/app/**
		/$1

Fastest JavaScript framework

Simon — Tue, 28 Jun 2011 03:40:41 +0000

I had to implement what I call a “row selector” for a web application.

It looks something like this (try it out by clicking the checkboxes in the first column):

Now, the tricky part is that this should work for large documents, say 500 rows.

I have implemented this with jQuery, Prototype, MooTools and pure JavaScript, and these are the results I get when toggling all 500 rows in IE8 on a Windows box with 512MB RAM:

jQuery 1.6.1: 2000ms
Prototype 1.7.0: 2450ms
MooTools 1.3.2: 6300ms (first toggle) / 1100ms
JavaScript: 250ms

These are some numbers for Firefox 5, running on the same machine:

jQuery 1.6.1: 150ms
Prototype 1.7.0: 120ms
MooTools 1.3.2: 230ms
JavaScript: 100ms

We have to support IE, so choosing the pure JavaScript version was a no-brainer.

Here are the results for the jQuery version on an iMac with 2GB RAM:

Google Chrome 12: 380ms
Safari 5: 150ms
Firefox 5: 140ms

It looks like Chrome is falling behind…

Try it out for yourself: jQuery, Prototype, MooTools and JavaScript.

CSS only drop-down menus (with submenus)

Simon — Sun, 26 Jun 2011 15:48:59 +0000

Who needs JavaScript to do drop-down menus on a HTML web-page? Anyway, I gave it a try.

This does not work in IE6, since I’m using the child selector and the :hover pseudo class. Personally, I think that we should stop supporting IE6, so that we can all focus on other things.

I’m using a CSS IE hack below since IE doesn’t do inline-block on block elements.

With the following HTML:


	Meat
	Vegetables
	Fruit and lots of fruit
		
			Organge
			Apple
				
					Fuji
					Gala
					Granny Smith
						
							Red
							Green
						
					
				
			
			Pomgranade

just add this CSS:

.navbar, .navbar ul {
	list-style-type: none;
	margin: 0;
	padding: 0;
}

.navbar li {
	position: relative;
	padding: 0.5em;
	white-space: nowrap;
}

.navbar > li {
	display: inline-block;
	zoom: 1;
	*display: inline;
}

.navbar ul {
	display: none;
	position: absolute;
	left: 0;
	top: 100%;
}

.navbar li:hover > ul {
	display: block;
}

.navbar ul ul {
	left: 100%;
	top: 0;
}

If you put it all together, this is what it looks like, with a tiny theme added: